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I have a couple of these DC motors

http://www.pololu.com/product/2202

Which have an extended motor shaft that sticks out the back and is 1mm diameter.

I'm having trouble trying to think of the best way to attach an encoder disk to this shaft.

I thought of getting a custom wheel 3d printed and make the opening 0.9mm so it will be a tight fit. But I don't know if is just to small?

I also though of taking the encoder disks from a PC mouse and drilling a 1mm / 0.9mm but its the same problem but with the added difficultly of trying to drill a small hole on a small thing.

So I wondered if anyone knows a better way, or of a made disk to attach. As I just can't find anything for a 1mm shaft

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  • $\begingroup$ It's not that difficult to drill a 1mm hole. The problem is being this on the motor shaft the acceleration they will suffer are high, just friction maybe don't fix it in place. A small portion of glue as mentioned could solve, but could present balance problem too. So if you could "print" it its a nice way, you could make the bore longer and so put glue inside it. $\endgroup$
    – Diego C Nascimento
    Jan 29, 2014 at 16:45

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  1. Place a disk on the large shaft.

  2. Depends how 'professional' you want to be.

A 1mm hole is not unreasonably hard to drill using a small hobby drill press, and you can do it with many battery drills with due care - the chuck minimum drill size is the main limitation. Down to about 0.8mm is easily enough achievable by mere mortals.

Substitute imperial units below if the mood seizes you.

(2a) You can push the 1mm shaft into material that it will penetrate and glue it in place with either epoxy or a super super-glue. Go from there.

(2b) If you get a piece of say 4mm dia brass rod you can -
File one end flat - repeat until good enough.
Mark centre - many guides how to do this on net.
Centre punch centre
Drill 1mm hole in end. Drill in horizontal clamp may help. Or not. Drill and tap to 2mm or 2.5mm a hole at right angles to long axis.
Add grub screw or screw - 2 or 2.5mm to suit.
You now have a shaft extension and half a coupler. Use other end as seems good.

(3) Mark a dark line on shaft. Use optical reflective detector to produce tach signal.

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